What size is your upstairs system both furnace and AC?

Obviously you are being oversized on the furnace quote but probably because you need a three ton blower in furnace and I don't believe you can get a smaller furnace in that Mdl that has a three ton blower. Discuss with dealer and find out what if any are your options.

If you stay with that furnace Mdl, I would want the Carrier Edge Thermidistat.

Any plans on a box filter cabinet?

IMO

A 2-stage AC helps in areas that suffer from high humidity. The 2-stage condenser only comes in whole tons so you have to move up to a 3 ton unit. In addition you have to get a variable speed furnace. It is a significant increase in price. It is probably not worth the extra cost.

A 16 SEER unit is often the best value for most parts of the country. A more efficient condenser will also require a variable speed furnace. I think Texas as reasonable electric rates so I don't think it is worth paying significantly more money for better efficiency.

Some detective work turned up original brochures on upstairs system! (Don't think I've seen them, ever)

All installed 6/28/96:
--Furnace is a Lennox G24M (m/n G24M2-45A4, s/n 6396D45846)
--A/C is a 2-ton Lennox Value 12 (12ACB24-3P, s/n 5896A46254)

So the furnace is 44K BTU/h?

I had no plans for a box filter cabinet; closet-sizewise the system has an EZ-filter base for a 16x25x1.

I may be oversizing the upstairs in any case. If I were replacing both floors, $11K seems like a large amount for 2100sqft, though I don't have a load calc in hand and don't know about the insulation. The home needs to be a lot more airtight but tends to hold temperatures better than I'd expect, considering.

I think summers around here are getting a lot more arid (and hotter overall).

So is it likely I was looking too big for no good reason, in thinking of replacing the 2-ton with a 2.5-ton? Perhaps "rightsizing" at 2 tons, single stage, would help with furnace sizing as well ...

Why upsize from 2 to 2.5 tons? I am not against increasing capacity when it is necessary and confirmed by a load calc, but was there ever a cooling problem when the system worked properly? 1000 sqft shouldn't need 2.5 tons. Ductwork should be sealed and insulated completely.. Oversizing decreases humidity control. I somewhat disagree with the tech's opinion that a 2-stage system would run on high stage all the time. When sized and set up properly. this is not true. Think about the milder days where you need better humidity control without full cooling capability. 2-stage systems are an improvement, though those which feature a Copeland Ultratech scroll compressor (most including all Carrier) have a net capacity of around 75% on low stage. So yes, there is not a huge drop off but considering most systems are oversized to begin with, the longer runtimes in low stage and the lowered airflow will *tend to* result in a quieter, more efficient system with more even comfort throughout the home. If a load calculation (which should be performed) reveals that a 2 ton will meet the upstairs' load needs, then a 3 ton two-stage system would be a mistake and negate the advantages a properly sized 2-stage system has to offer.

This post was edited by ryanhughes on Thu, Jun 6, 13 at 19:06